The present invention relates to improved pre-collation copying systems and to improved automatic document handling systems therefor providing pre-collation copying from duplex documents.
As xerographic and other copiers increase in speed, and become more automatic, it is increasingly important to provide higher speed yet more reliable and more automatic handling of both the copy sheets and the individual original documents being copied. Yet, it is desired to accommodate original documents and copy sheets which vary widely in size, weight, thickness, material, condition, humidity, age, etc. It is desirable to automatically handle such individual document and copy sheets in rapid succession with relatively compact and inexpensive sheet handling apparatus. Further, it is desirable to provide sheet handling systems and apparatus which accommodates different sheet orientations and movement directions so as to be able to optimize and compact the design of the copier and/or its document handling unit. The providing of duplex copying capabilities and/or a pre-collation copy system greatly complicates and increases these copier sheet handling difficulties.
The term "duplex copying" may be more specifically defined into several different, individually known, copying modes. In duplex/duplex copying, both sides of a duplex document sheet (which has images on both sides) are copied onto both sides of a single copy sheet. In duplex/simplex copying, both sides of a duplex document are copied onto only one side of two successive copy sheets. In simplex/duplex copying, the images on one side of two successive simplex documents are placed on opposite sides of a single copy sheet. In the printing industry, as opposed to the copier industry, two-sided copying may be referred to as "backing-up" rather than duplex copying.
In a set of duplex documents or copy sheets, pages 1, 3, 5, etc., will typically appear on one side, with pages 2, 4, 6, etc., on the other side. Thus, they may be respectively referred to as the "odd order" and "even order" sides.
The duplex copying of the copy sheets for duplex/duplex or simplex/duplex copying may be done by first making a set of simplexed copy sheets (printed only on their first sides) temporarily storing these simplex copy sheets in a tray, and then feeding them back through the copying processor for a second pass printing of the opposite order document images on the opposite sides of the copy sheets. Such systems may be referred to as sequential or dual pass duplexing systems. Examples of such systems for handling the copy sheets being duplexed are shown in U.S. Pat. Nos. 3,615,129, issued Oct. 26, 1971, to W. A. Drawe, et al., and 3,645,615, issued Feb. 29, 1972, to M. R. Spear, Jr., and in the Xerox 4000 and 4500 Copiers. Of particular interest as disclosing the preferred simplex/duplex pre-collation copying system disclosed herein is a U.S. Pat. No. 4,116,558, issued Sept. 26, 1978, based on application Ser. No. 767,012, filed Feb. 9, 1977, by J. A. Adamek et al. Column 7, first paragraph thereof discusses duplex/duplex copying. These dual pass duplex systems have the advantage of being able to utilize a single, conventional, imaging station, transfer station, and processor for both sides of the copies.
Alternatively, a single pass or simultaneous duplex system may be used in which unfused images are transferred to both sides of the copy sheet in a single pass, simultaneously or in immediate sequence, and the first and second sides of each document are copied simultaneously or in immediate sequence (serially). An example of such a single pass duplex system is disclosed, for example, in U.S. Pat. No. 3,844,654 issued Oct. 29, 1975 to J. Guenther and the art cited therein. However, such systems typically disadvantageously require two separate imaging, image development, and transfer systems.
The present invention is particularly directed to pre-collation duplex copying systems in which the image sources are a set of original duplex document sheets, with images on both sides thereof, in which these duplex documents are automatically multiply recirculated with automatic exposure of both sides of the documents so as to provide pre-collated copy sets therefrom.
A highly desirable feature for a copier is to provide automatic document recirculation for pre-collation copying. As discussed, for example, in detail in U.S. Pat. No. 3,963,345 issed June 15, 1976, to D. J. Stemmle, et al., at Column 1-4, such pre-collation copying systems provide a number of important advantages. The copies exit the copier in pre-collated sets, and do not require subsequent sorting in a sorter or collator. Any desired number of such copy sets may be made by making a corresponding number of recirculations of the document set in collated order past a copying station and copying each document once each time it recirculates. On-line finishing and/or removal of completed copy sets may be provided while additional copy sets are being made from the same document set.
However, a disadvantage of pre-collation copying systems is this fact that the documents must all be repeatedly circulated and repeatedly individually copied the number of times equivalent to the desired number of copy sets. Thus, for example, to make 10 copy sets of a 5 page simplex document set or book, one copy at a time would be made of each of the 5 document pages in this order: Pages 1, 2, 3, 4, 5; 1, 2, 3, 4, 5, etc.; repeated a total of 10 times (10 circulations) to make the desired 10 copy sets. [For bi-directional pre-collation copying this document copying sequence would, instead, be 1, 2, 3, 4, 5; 5, 4, 3, 2, 1; 1, 2, 3, 4, 5; etc.] Thus, it may be seen that increased document handling is necessitated for a pre-collation copying system, as compared to a conventional post-collation copying system in which all the desired copies are made at one time from each document page and collated subsequently. In such a post-collation copying system, the document set need only be circulated once to fill the bins of the copy sheet sorter or collator with the number of copy sets desired (limited in number, however, by the number of available bins).
The increased document handling required for a pre-collation copying system increases the liklihood of document damage or wear, and particularly aggravates the problems of document separation where the individual documents must be separated from the remainder of the documents in the document set for each recirculation thereof. Thus, it is highly desirable to have a simple and reliable document handling system and recirculation path for the document in all modes of operation.
The present invention is intended to overcome or minimize the above-discussed problems and disadvantages and provide the advantages of pre-collation copying. It provides a simple, compact, automatic pre-collation document handling system, in which the document set may be maintained in a compact manner, and recirculated in a short and simple document handling path, to minimize document damage and to maximize the ability to reliably multiply circulate and copy different or defective documents. The system disclosed herein is particularly suitable for, and compatible with, conventional copier platens and optics systems. It is also suitable for use as a removable or auxiliary document handling system, removably overlying an existing or conventional copier platen to selectively allow use of that same platen and its associated optics for manual or other non-pre-collation copying. However, it is not limited thereto.
The method and apparatus disclosed herein is believed to be the first practical system detailed for the automatic selective pre-collation copying of either duplex or simplex document sheets onto pre-collated duplexed copy sheet sets utilizing conventional single imaging, development and transfer copier stations. There is disclosed herein a system whereby a copier may utilize the same automatic document recirculation and copy sheet handling systems to provide pre-collated copy sets in duplex/duplex, duplex/simplex, simplex/duplex, and simplex/simplex copying modes, thus providing all possible pre-collation copying modes from document sheets.
Some examples of art relating to pre-collation document handling systems in which a document is withdrawn from the bottom of a document set stack for copying, imaged at an imaging station, and then returned to the top of the stack, i.e. the original documents are multiply recirculated to and from the stack of documents, include: U.S. Pat. No. Re. 27,976, (originally U.S. Pat. No. 3,499,710, issued Mar. 10, 1970) to L. W. Sahley; U.S. Pat. No. 3,536,320, issued Oct. 27, 1970, to D. R. Derby; U.S. Pat. No. 3,552,739, issued Jan. 5, 1971, to R. R. Roberts, et al.; U.S. Pat. No. 3,556,511, issued Jan. 19, 1971, to A. Howard, et al.; U.S. Pat. No. 3,888,579, issued June 10, 1975 to V. Rodek et al.; and U.S. Pat. No. 3,937,454, issued Feb. 10, 1976, to R. H. Colwill. A recent precollation copying system of this type is shown in Belgium Pat. No. 835,568 laid open May 13, 1976, and West German patent application No. 2,550,985 published May 26, 1976, and French application Publication No. 2,291,131, laid open Nov. 12, 1976, all based on U.S. application Ser. No. 523,610 filed Nov. 13, 1974 apparently refiled Jan. 8, 1976 as Ser. No. 647,683. A disclosure similar to the latter is in U.S. Defensive Publication No. T957,006 of Apr. 5, 1977, based on application Ser. No. 671,865, filed Mar. 30, 1976, by M. G. Reid, et al. The systems shown in these latter cited applications also disclose other features of interest to the present application.
U.S. Pat. No. 2,822,172 issued Feb. 4, 1958 to C. R. Mayo et al. discloses a pre-collation copier with a vacuum drum holding and moving the documents for imaging.
It is known to multiple recyclingly copy the same side of a single individual document in a non-precollation copying system wherein the recycling path length may be changed to accommodate different sizes of documents, as shown in U.S. Pat. No. 3,409,366, issued Nov. 5, 1968, to W. J. Hanson, et al. There a movable deflector finger in the document path selects between the two partially different document circulation paths.
The general concept of imaging a document while it is on a vacuum or frictional surface drum, which drum also serves to invert the document for subsequently copying the second side thereof, i.e., as part of a duplex document copying system, is disclosed, for example, in the above-cited U.S. Pat. No. 3,844,654, issued Oct. 29, 1974, to J. Guenther. Note there drum 44, described in column 4. Also noted in this regard are U.S. Pat. Nos. 3,227,444, issued Jan. 4, 1966, to J. F. Egan; and 3,506,347, issued Apr. 14, 1970, to C. F. Carlson (note FIG. 4).
Other examples of non-pre-collation copying systems with roller or other inverting systems in a document path for inverting duplex documents so that the opposite sides thereof may be imaged are shown in IBM Technical Disclosure Bulletins Vol. 14, No. 5, October 1971, p. 1547; and Vol. 19, No. 12, May 1977, p. 4496. Another is U.S. Pat. No. 3,862,802 issued Jan. 28, 1975, to H. R. Till.
Of particular interest, as disclosing a means for selectively inverting or not inverting a document in a copying path, for copying one side of a document on one pass and the other side of that document on the next pass, is the system shown particularly in FIG. 6 and described at Cols. 5-6 in U.S. Pat. No. 4,040,616 issued Aug. 9, 1977 by S. G. Clarkson et al.
An example of a copier control system and logic circuitry in which the systems disclosed herein may be incorporated is described in U.S. Pat. No. 3,936,182, issued Feb. 3, 1976, to Sikander Sheikh. While integral software incorporation into the copier's general logic circuitry and software, as in that patent, of the functions and logic defined herein is preferred, the functions and systems disclosed herein may be conventionally incorporated into a copier utilizing any other suitable or known software or hard wired logic system or microprocessor or known cam-bank switch controllers for copiers. The control of the exemplarly systems disclosed herein may be accomplished by activating known electrical selonoid control sheet deflector fingers and drive motors or their clutches in the indicated sequences and does not require unconventional sheet handling hardware or controls. Conventional sheet path position and jam sensor switches may be utilized.
By way of background as to details of particular sheet handling apparatus disclosed herein, an example of a stacking tray with a bottom retard sheet feeder and a normal force applicator therefor is disclosed in U.S. Pat. No. 4,014,537, issued Mar. 29, 1977, to K. K. Stange. Bottom air flotation (which to a certain extent will affect the normal force requirements) is also disclosed there. The use of a foraminous impact or bounce pad for reversing the direction of motion of a sheet in a duplexing system is shown in U.S. Pat. No. 3,856,295, issued Dec. 24, 1974 to John H. Looney. In regard to the use of a continuously rotating jogging or stacking member to compile sheets in a stack against a registration edge there is noted by way of example a U.S. Pat. No. 3,709,595, issued Jan. 9, 1973, to L. H. Turner, et al.
All of the patents cited herein for art purposes are also incorporated by reference herein to the extent they provide teachings of usable or alternative systems or hardware for the disclosed embodiments herein.
Exemplary embodiments of the present invention are shown and described hereinbelow incorporated into an otherwise conventional exemplary xerographic apparatus and process. However, it is not limited thereto. The xerographic apparatus and process itself need not be described herein since various known patents, texts and commercial apparatus are available to provide further details thereof to those skilled in the art, including patents cited above. For example, the disclosed document handling system may be utilized with various copier optics and copy sheet handling systems and processing systems in addition to those disclosed herein.